The present invention relates to cutting tools and, in particular, it concerns a modular cutting tool assembly in which cutting inserts with different cutting point nose angles may be used interchangeably.
It is known to employ cutting inserts made of various hard materials which have polygonal, round, or otherwise rotationally symmetric cutting edges mounted in a receiving pocket of the tool holder of a cutting tool. During a machining operation (turning, milling, etc.), a portion of the available cutting edge cuts the workpiece, typically along edges adjacent to a cutting point. When the cutting edges adjacent to one point of a regular insert have been worked, the insert is indexed to present a whole new cutting point.
Many different forms of cutting inserts are commonly used. In turning operations, for example, one of the primary criteria for selecting an appropriate insert type is the nose angle required. In order to define the term "nose angle", it should be noted that most cutting points as seen in plan view are made up of two straight or low-curvature lines meeting at a point, sometimes modified by rounding to a relatively small nose radius in the point region. The angle which would be made between the straight or low-curvature lines, disregarding the rounding of the point itself, is referred to herein as the "nose angle". The nose angle so defined generally has a well defined value for any cutting insert with the notable exception of round inserts in which the nose radius becomes the radius of the entire insert cutting geometry.
A range of nose insert angles are conventionally provided by cutting inserts of various different overall shapes as indicated in FIG. 1. Near 90.degree. angles are provided by "S" type square inserts. Eighty degree cutting points are provided by "Q" type concave-sided square, "W" type convex triangle or "Trigon", and "C" type diamond. Sixty degree cutting points are provided by "T" type triangular inserts. Smaller nose angles are typically provided by diamond shapes such as the 55.degree. "D" type and 35.degree. "V" type, or by the "K" type 55.degree. parallelogram.
Clearly, the requirements for effectively restraining these different types of cutting insert within a pocket are highly specific to the geometry of the cutting edge. Thus each type of insert is provided with a dedicated tool holder design with a corresponding pocket shape. As a result, the use of multiple insert types is accompanied by the expense of providing and storing multiple tool holders, and necessitates the additional labor of exchanging the entire tool between cutting operations.
In an attempt to reduce these costs and labor, modular systems based on replaceable cartridges have been developed. These systems employ replaceable adapter cartridges each of which provides a pocket with clamping geometry suited to a specific cutting insert. Although these systems do allow the primary tool holder to be used with different cutting insert types, the replacement of the cartridges still adds a wasteful additional dissembly/assembly step to the changeover.
There is therefore a need for a modular cutting tool assembly which allows alternate use of multiple cutting inserts with differing nose angles within a single tool holder pocket. There is also a need for cutting inserts and tool holders for use in such an assembly.